/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.juli;

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.TimeUnit;
import java.util.logging.LogRecord;

/**
 * A {@link FileHandler} implementation that uses a queue of log entries.
 * <p>
 * <p>Configuration properties are inherited from the {@link FileHandler}
 * class. This class does not add its own configuration properties for the
 * logging configuration, but relies on the following system properties
 * instead:</p>
 * <p>
 * <ul>
 * <li><code>org.apache.juli.AsyncOverflowDropType</code>
 * Default value: <code>1</code></li>
 * <li><code>org.apache.juli.AsyncMaxRecordCount</code>
 * Default value: <code>10000</code></li>
 * <li><code>org.apache.juli.AsyncLoggerPollInterval</code>
 * Default value: <code>1000</code></li>
 * </ul>
 * <p>
 * <p>See the System Properties page in the configuration reference of Tomcat.</p>
 *
 * @author Filip Hanik
 */
public class AsyncFileHandler extends FileHandler {

	public static final int OVERFLOW_DROP_LAST = 1;
	public static final int OVERFLOW_DROP_FIRST = 2;
	public static final int OVERFLOW_DROP_FLUSH = 3;
	public static final int OVERFLOW_DROP_CURRENT = 4;

	public static final int OVERFLOW_DROP_TYPE = Integer.parseInt(System.getProperty("org.apache.juli.AsyncOverflowDropType", "1"));
	public static final int DEFAULT_MAX_RECORDS = Integer.parseInt(System.getProperty("org.apache.juli.AsyncMaxRecordCount", "10000"));
	public static final int LOGGER_SLEEP_TIME = Integer.parseInt(System.getProperty("org.apache.juli.AsyncLoggerPollInterval", "1000"));

	protected static LinkedBlockingDeque<LogEntry> queue = new LinkedBlockingDeque<LogEntry>(DEFAULT_MAX_RECORDS);

	protected static LoggerThread logger = new LoggerThread();

	static {
		logger.start();
	}

	protected volatile boolean closed = false;

	public AsyncFileHandler() {
		this(null, null, null);
	}

	public AsyncFileHandler(String directory, String prefix, String suffix) {
		super(directory, prefix, suffix);
		open();
	}

	@Override
	public void close() {
		if (closed) return;
		closed = true;
		super.close();
	}

	@Override
	protected void open() {
		if (!closed) return;
		closed = false;
		super.open();
	}

	@Override
	public void publish(LogRecord record) {
		if (!isLoggable(record)) {
			return;
		}
		LogEntry entry = new LogEntry(record, this);
		boolean added = false;
		try {
			while (!added && !queue.offer(entry)) {
				switch (OVERFLOW_DROP_TYPE) {
					case OVERFLOW_DROP_LAST: {
						//remove the last added element
						queue.pollLast();
						break;
					}
					case OVERFLOW_DROP_FIRST: {
						//remove the first element in the queue
						queue.pollFirst();
						break;
					}
					case OVERFLOW_DROP_FLUSH: {
						added = queue.offer(entry, 1000, TimeUnit.MILLISECONDS);
						break;
					}
					case OVERFLOW_DROP_CURRENT: {
						added = true;
						break;
					}
				}//switch
			}//while
		} catch (InterruptedException x) {
			//allow thread to be interrupted and back out of the publish operation
			//after this we clear the flag
			Thread.interrupted();
		}

	}

	protected void publishInternal(LogRecord record) {
		super.publish(record);
	}

	protected static class LoggerThread extends Thread {
		protected boolean run = true;

		public LoggerThread() {
			this.setDaemon(true);
			this.setName("AsyncFileHandlerWriter-" + System.identityHashCode(this));
		}

		@Override
		public void run() {
			while (run) {
				try {
					LogEntry entry = queue.poll(LOGGER_SLEEP_TIME, TimeUnit.MILLISECONDS);
					if (entry != null) entry.flush();
				} catch (InterruptedException x) {
					Thread.interrupted();
				} catch (Exception x) {
					x.printStackTrace();
				}
			}//while
		}
	}

	protected static class LogEntry {
		private LogRecord record;
		private AsyncFileHandler handler;

		public LogEntry(LogRecord record, AsyncFileHandler handler) {
			super();
			this.record = record;
			this.handler = handler;
		}

		public boolean flush() {
			if (handler.closed) {
				return false;
			} else {
				handler.publishInternal(record);
				return true;
			}
		}

	}


}
